Phase III study of androgen deprivation therapy (ADT) with enzalutamide (ENZA) or placebo (PBO) in metastatic hormone-sensitive prostate cancer (mHSPC): The ARCHES trial.

Abstract

687 Background: ENZA, a potent androgen receptor inhibitor, has demonstrated benefit in men with metastatic and nonmetastatic castration-resistant prostate cancer (CRPC). Efficacy of ENZA with ADT in men with mHSPC is unknown. Methods: ARCHES is a multinational, double-blind, phase 3 study (NCT02677896). Patients (pts) with mHSPC were randomized 1:1 to ENZA (160 mg/day) + ADT or PBO + ADT, stratified by disease volume (CHAARTED criteria) and prior docetaxel therapy. Primary endpoint was radiographic progression-free survival (rPFS) assessed centrally or death within 24 weeks of treatment discontinuation. Secondary endpoints included time to prostate-specific antigen (PSA) progression, PSA and radiographic responses and overall survival (OS). Treatment continued until disease progression or unacceptable toxicity. Results: 1150 men were randomized to ENZA (n=574) or PBO (n=576); baseline characteristics were balanced between groups. Overall, 67% had distant metastasis at initial diagnosis; 63% had high volume disease, 18% had prior docetaxel. Median follow-up was 14.4 mo. ENZA + ADT significantly improved rPFS (Table); similar significant improvements in rPFS were reported in prespecified subgroups of disease volume, pattern of spread, region and prior docetaxel (HRs 0.24–0.53). Secondary endpoints improved with ENZA + ADT (Table); OS data are immature. Grade 3–4 adverse events (AEs) were reported in 23.6% of ENZA pts vs 24.7% of PBO pts with no unexpected AEs. Conclusions: ENZA + ADT significantly improved rPFS and other efficacy endpoints vs PBO + ADT in men with mHSPC, with a preliminary safety analysis that appears consistent with the safety profile of ENZA in previous CRPC clinical trials. Acknowledgements: Medical writing and editing assistance was provided by Stephanie Rippon, MBio, and Lauren Smith from Complete HealthVizion, funded by the study sponsors. This study was funded by Astellas Pharma Inc. and Medivation LLC, a Pfizer Company, the co-developers of enzalutamide. Clinical trial information: NCT02677896. [Table: see text]